The present invention refers to a barrel assembly for firearms and to a method for manufacturing it.
As is known, multi-barreled shotguns, such as for example over-and-under or side-by-side shotguns for hunting and target shooting, have barrels which are mutually joined at the breech by means of the so-called demi-block, or chopper-lump, system, or by means of a mono-block.
In the demi-block system, two separate tubes of a set of barrels are joined together, where the right-hand half of the pair of lumps under the barrels are forged integrally with the right barrel and the left-hand half of the pair of lumps under the barrels are forged integrally with the left barrel.
In the mono-block system the entire breech end of both barrels and the lumps together are machined from one solid piece of steel. The barrel tubes are then fitted separately into a mono-block and the ribs attached.
In order to fix the tubes to the mono-block, each tube has a shank which is inserted in a respective cylindrical seat formed inside the mono-block, which of course has two superimposed seats.
The assembly constituted by the mono-block, the tubes and the ribs form the double barrel of the shotgun.
The extractors are mounted on the assembly and the finishing work, which consists in providing the cartridge chambers with the corresponding rims, is performed.
The assembly subsequently undergoes stress relieving in a furnace because of to the need to weld the ribs and any other components.
Subsequent reworking is therefore necessary and includes the localized heat treatment of the regions of the sleeve that are most intensely stressed during firing.
Some regions of the sleeve, however, are not treated adequately and can have a lower than desired strength, for example in the chamber seats, in the extractor seats, and in the extractor head seats, where these devices will be inserted.
With use, the seats become worn and after some time it is necessary to recondition the weapon; this work can be performed only by specialized personnel capable of performing the necessary machining of the seats that accommodate the new mechanisms or devices.
US-A-2006/0207154 discloses a multi-barreled shotgun barrel assembly construction constituted by a muzzle block, an extended chopper block, and barrel tubes, that join the two blocks. While the barrel tube manufacturing is simplified, such barrel construction introduces a further component, the muzzle block, that requires a precise working. Also, the extended chopper block requires the same type of working of a conventional chopper block.